a ae 
1903] FLORA OF SOUTHERN CALIFORNIA 275 
REGIONAL AFFINITIES OF THE FAMILIES. 
TROPICAL AND SuB- 
nea CosMOoPoLITAN EXTRATROPICAL TROPICAL 
CATEGORIES 
Families Per cent, Families Per cent. Families Per cent. 
Gamopetalae....... 12 37 8 25 12 27 
Choripetalae....... 24 38 21 33 18 wkd 
Dicotyledones...... 36 38 29 30 30 3! 
Monocotyledones... 12 70 a II 3 17 
Angiospermae...... 48 43 31 28 33 29 
Gymnospermae..... fe I 50 . 5° 
Spermatophyta... 48 43 32 - 28 34 mt 4 
Pteridophyta....... 4 57 I 14 2 28 
TOPAR cc n gs 52 PE 33 27 36 30 
In the next table are exhibited the relations of the native 
genera and species to the flora of North America. The number 
of each which extend beyond the North American continent is 
shown; and those which are confined to it are separated into 
four geographical subdivisions; namely, those whose range is 
restricted respectively to southern California, to California, to 
the region west of the Rocky Mountains, and those which extend 
further eastward. While the line has been drawn very strictly 
between plants which are or are not exclusively North American, 
and as accurately as possible for those confined to western North 
America, a somewhat laxer rule has been observed for the two 
smaller subdivisions. These are merely political, and have little 
phytogeographical significance, and the limits of many of their 
plants as yet are not known accurately. For these reasons there 
are included in the number accredited to California, and to 
southern California, some plants which, while properly belonging 
to them, extend a little beyond their boundaries. 
This table brings out very clearly the distinctively west 
American character of the flora. Two-thirds of the genera, it 
is true, extend their range beyond North America; but of the 
remaining one-third, only 14 per cent. are found east of the 
ocky Mountains, while 86 per cent. of this third are con- 
fined to the territory west of them, and of these about half 
